1. Field of the Invention
The present invention generally relates to electronic devices and integrated circuits (ICs) and their methods of manufacture, and more particularly, structures and methods for forming bipolar transistors.
2. Background of the Invention
Bipolar transistors are much used in modern electronic devices, especially integrated circuits (ICs). However, their performance is sometimes less than ideal, especially when they are being manufactured using a process optimized for other types of devices that may be the principal devices in the IC of which the bipolar transistor is to be a part. Metal-oxide-semiconductor field effect transistors (MOSFETs) and complementary metal-oxide-semiconductor (CMOS) field-effect-transistors (FETs) are non-limiting examples of such other devices widely used in ICs. However, the present invention is not limited merely to ICs made primarily using MOSFETs, CMOS devices and/or FETs but also applies to other device structures and associated manufacturing methods. Where bipolar transistors need to be included in the IC, they are often made using whatever process steps are available for making the device types that form the principal devices in the IC. In these circumstances, the properties of the bipolar transistors fabricated using unmodified manufacturing processes for such other device types are often less than ideal. While the properties of the included bipolar transistors might be improved by modifying and/or adding to the available process steps this will generally increase the overall cost of manufacture of the whole IC, which is very undesirable. Accordingly, a need continues to exist for providing improved bipolar devices adapted to be included in ICs with other types of devices without significantly modifying the underlying IC manufacturing process.